KR20040088497A - Method and apparatus for avoiding duplicate negotiations during communication establishment - Google Patents

Abstract

The network element 204, which acts as an intermediary between two peers 202 and 206, monitors the control messages exchanged between the two peers when establishing a point-to-point protocol session. Relevant parameters in such control messages are stored 612 for later use. When retransmitted control messages are detected (610), the network element processes the retransmitted control message based on the stored parameters 618, so that additional negotiation loops are avoided. In this way, the effects of asynchronous link establishment and different timeout timers are mitigated by the network element.

Description

Method and apparatus for avoiding duplicate negotiations during communication establishment

Wireless communication systems are well known in the art. Such systems typically include multiple mobile subscribers (MSs) or communication units within a wireless communication system with an infrastructure. As is known in the art, Point-to-Point Protocol (PPP) is typically used to establish communication between two peers. Typically, the peer is implemented as a logical process executed by the physical platform representing the peer. Once peer-to-peer communication is established, data is transferred between communication units and another device to implement a destination peer within the infrastructure via one or more intermediate network elements. This is shown in FIG.

In particular, FIG. 1 shows protocol stacks according to the so-called Open Systems Interconnection (OSI) model. As shown, the protocol stacks of the communication unit (on the left), the network element (on the middle), and the interaction unit (IWU) (on the right) are shown. As is known in the art, the individual layers within protocol stacks terminate logically, not physically, within corresponding levels of other protocol stacks. For example, the physical layer 102 is provided between the network element and the IWU. Similarly, different physical layer protocols are implemented between network elements and communication units, in particular the so-called IS95 / IS2000 protocol. Other protocol layers known to those skilled in the art are also shown in FIG. In particular, the PPP layer 110 is terminated by the communication unit and the IWU. Note that while the network element actively converts low level protocol stacks, it transparently passes data about the PPP layer 110 as indicated by the bold arrow. Consecutive upper layers of each protocol stack in the communication unit and the IWU are built on the PPP layer. For example, the Internet Protocol (IP) layer 112 and other upper layers 114 exchange information through the point-to-point protocol layer 110.

As is known in the art, when a PPP connection is established, each peer is involved in a time-sensitive negotiation of the link before passing data. Examples of optimal negotiations are shown in FIG. As shown, the communication unit 202 communicates with the IWU 206 via one or more network elements 204. Note that in Figure 2, time progression from the top to the bottom is shown. In an ideal scenario, the communication link between the IWU 206 and the network element 204 as well as the communication link between the communication unit 202 and the network element 204 are established substantially simultaneously as shown by the bold arrows in FIG. 2. These negotiations then include the transmission by each peer of the configuration request message REQ prior to the timely transmissions of the acknowledgment messages ACK as shown in FIG. In this description, if acknowledgments before expiration of the timeout timer are initialized after the request messages have been transmitted, these acknowledgments are sent in a timely manner. A typical timeout timer 208 is shown schematically in FIG. In this case, the timeout timer 208 is initialized by the communication unit 202 immediately after sending the configuration request to the IWU 206. If an acknowledgment sent by the IWU to the communication unit is received by the communication unit before expiration of the timeout timer 208, the negotiation is successfully completed for the communication unit. A similar process is applied to IWU 206 based on its timeout timer (not shown). If a given peer does not receive a confirmation before expiration of the timeout timer, it restarts the negotiations by resending the configuration request. Typically, PPP is used in a wireless environment where link establishment is performed between peers after the physical connection is fully established, and the likelihood of any impact due to different timeout timers between peers becomes relatively low.

However, in the real world of real wireless systems, links between peers and network elements are not always established at the same time. Thus, the timing of the request / acknowledge exchange may be disrupted to the point where additional, often time multiple negotiation loops must occur. In addition, different peers in a communication system may be configured with timeout timers of different durations. Thus, sometimes unpredictable delays caused by the transmission of requests and / or acknowledgments across an intermediate network can cause negotiations to fail if a given timeout timer is not configured to accommodate such delays. Again, this result is typically one or more negotiation loops. The occurrence of such negotiation loops adversely affects the build time required to establish communications between peers. Since the overall quality of the communication system is determined in part by the speed with which communication is established, the occurrence of multiple negotiations results in poor quality perceived by users of the communication system.

The present invention relates generally to wireless communication systems and, more particularly, to a technique for establishing communications based on point-to-point protocols in such systems that avoid redundant negotiations.

1 schematically illustrates the relationship between protocol stacks within various elements of a communication system according to the prior art;

2 is a timing diagram illustrating optimal negotiations of a point-to-point protocol.

3 is a block diagram of a wireless communication system in accordance with the present invention.

4 is a timing diagram illustrating the occurrence of redundant negotiations resulting from asynchronous construction of communication links.

5 is a timing diagram illustrating the occurrence of redundant negotiations in accordance with different timeout timers.

6 is a flow chart illustrating a method of avoiding redundant negotiations when establishing inter-peer communications in accordance with the present invention.

7 and 8 are timing diagrams showing further embodiments of the operation of the present invention.

Thus, it is useful to provide a technique that substantially avoids redundant negotiations when establishing PPP communications.

The present invention provides a technique for establishing a PPP session to substantially avoid duplicate negotiation loops despite asynchronous link establishment or occurrence of different timeout timers. To this end, the network element acting as an intermediary between the two peers monitors the messages exchanged between the two peers. Control messages between these peers are identified and monitored, and the relevant parameters in such control messages are stored for later use. Monitoring control or data messages does not prevent the messages from going to their original destination. Then, when the network element detects a retransmission of the control message, it processes the retransmitted control messages based on the stored parameters to avoid the occurrence of additional negotiation loops. In the present preferred embodiment, the peers may comprise a communication unit and an interaction unit. In addition, in another embodiment of the present invention, the processing performed by the network element to avoid duplicate negotiation loops discards the retransmission of the control message and optionally sends a confirmation to retransmit the control message to the peer initiating the retransmission. It includes. In this way, the effects of asynchronous link establishment and different timeout timers are mitigated by the network element. The present invention can be explained more easily with reference to Figs.

Referring now to FIG. 3, there is shown a wireless communication system 300 in accordance with the present invention. In particular, the system 300 includes a number of mobile subscribers or communication units 302 that communicate with the intermediate wireless network 306 via radio resources 304. For any given call, the intermediate network 306 communicates with either a packet network 310 or a circuit network 314 that can be connected to a public network 350, such as the Internet or the World Wide Web. The communication system 300 shown in FIG. 3 is typically found in code division multiple access (CDMA) systems today. However, the present invention is not limited to being applied to such CDMA systems, but may be usefully applied to any wireless communication system that uses PPP to establish communications between a wireless peer and an infrastructure-based peer.

The communication units 302 may actually include any wireless device, but in a preferred embodiment include mobile and / or portable devices, such as in-vehicle two-way radios or portable wireless telephones. In any case, the communication units 302 communicate with the intermediate network 306 via the radio resources 304. In the present preferred embodiment, the radio resources 304 include RF channels that implement CDMA protocols. However, the present invention is not limited in this regard, and radio resources 304 may employ other types of access protocols as known in the art, such as frequency division multiple access (FDMA) or time division multiple access (TDMA) protocols. It may include other types of wireless channels that implement.

Intermediate network 306 includes a wireless front end of base transceiver systems 320 coupled to one or more base station controllers 324. Each base station controller 324 is then coupled to a mobile switching room 326 as is known in the art. The construction and operation of base transceiver systems 320, base station controllers 324, and mobile switching centers 326 are well known in the art and will not be described in further detail. As further shown in FIG. 3, each of the base station controller 324 and the mobile switching center 326 includes one or more processors 330, 340 coupled to the respective storage devices 332, 342. Each of these processors 330, 340 may include one or more microprocessors, microcontrollers, digital signal processors, combinations thereof, or other devices known to those skilled in the art. Likewise, each of the storage devices 332, 342 can include volatile and nonvolatile digital storage elements such as random access memory (RAM) and / or read-only memory (ROM) or their equivalents. In particular, the processor / storage combinations provided in the base station controller 324 and the mobile switching center 326 may be used to implement software algorithms stored in the storage devices 332, 342 and executed by the processor platforms 330, 340. Can be.

As shown, this known controller 324 is coupled to a packet network 310 that includes an IWU 308. Similarly, mobile switching room 326 is coupled to circuit switched network 314, which also includes IWU 312. As is known in the art, the IWU executes communications between the devices to which they are coupled (eg, base station controller or mobile switching center) and the network. In alternative embodiments, IWUs 308 and 312 may be implemented in devices such as a packet data service node (PDSN) or an access gateway, which devices are well known to those skilled in the art. Note that the base station controller 324 or mobile switching center are network elements that may implement the present invention. Finally, IWUs 308, 312 in packet and circuit switched networks may be coupled to a public network 350, such as the Internet or the World Wide Web.

As described above, the communication units 302 may establish communications with the IWUs 308, 312 via the intermediate network 306. To this end, PPP including any inter-peer protocol requiring bi-directional initialization may be used. Problems arising from asynchronous link establishment and different timeout timers and their effects on PPP establishment are additionally shown in FIGS. 4 and 5 respectively.

Referring now to FIG. 4, there is shown a timing diagram illustrating problems resulting from the occurrence of asynchronous link establishment. (Note that in Figures 4, 5, 7, and 8, as in Figure 4, the progression of time is shown from top to bottom). Especially. The communication unit 202 attempts to establish communication with the IWU 206 via the wireless element 204. However, the communication unit 202 has a link to the network element 204 that is established substantially after the link between the IWU 206 and the network element 204, as shown by the bold arrows. Since the link between the IWU and the network element is well established before the link between the communication unit and the network element, the IWU sends a request 402 after the peer process has been initiated, which request 402 establishes a link for the communication unit. As soon as it reaches the communication unit. However, since the peer process in the communication unit has not yet had a chance to initialize, the request message is ignored. Note that the IWU initializes the first timeout timer 408 and waits for a return of confirmation in response to the request 402 sent.

After the peer process of the communication unit is initialized, it sends its request message 404 to the IWU, and upon return, the IWU sends a confirmation 406 back to the communication unit. After receiving acknowledgment 406 of the IWU, the communication unit initializes a second timeout timer 410 to delay receipt of the configuration request from the IWU. Recall that the configuration request 402 originally sent by the IWU is ignored due to the early arrival of the communication unit. When the second timeout timer 410 expires, the communication unit assumes that it needs to restart the negotiation process to resend the configuration request 412. Likewise, upon expiration of first timeout timer 408, the IWU resends its configuration request 414. At this time, since each request is confirmed (416, 418), it is determined that the negotiation handshake (negotiation handshake) to continue the call establishment. However, additional negotiations and subsequent confirmations 416, 418 required for retransmissions of configuration requests 412, 414 substantially delay call establishment. Depending on the negotiation stage, such delays can be as high as a few milliseconds, for example up to 100 msec.-2 sec.

Referring now to FIG. 5, there is shown a timing diagram illustrating problems resulting from the occurrence of different timeout timer durations in separate peers. In this case, the links between the communication unit 202, the IWU 206 and the network element 204 are established substantially simultaneously as shown. Similarly, if peer processes are initiated in both the communication unit and the IW, configuration requests 502 and 504 are sent by each peer to another peer. Likewise, later, configuration requests 502 and 504 are sent in response to each request 502 and 504. However, in this case, the acknowledgment 508 sent by the IWU takes somewhat longer to transmit compared to the acknowledgment 506 sent by the communication unit. Various reasons, such as latency, retransmissions and processing delays of lower layers due to radio frequency loss, can contribute significant delays by the IWU in acknowledgment transmission.

In any case, upon sending the corresponding configuration request 502, 504, each peer also initializes a timeout timer, which waits for a configuration acknowledgment. In this case, however, the duration of the first timeout timer 510 in the communication unit is shorter than the duration of the second timeout timer in the IWU. This generates an acknowledgment 506 sent by the communication unit received by the IWU before expiration of the second timeout timer. Thus, the peer process in the IWU assumes that the initial link control face of the PPP is continuously initialized, and initiates the authentication phase by issuing the appropriate challenge 516. However, the shorter duration of the first timeout timer 510 becomes the acknowledgment 508 sent by the IWU, as shown, to reach the communication unit only after the first timeout timer 510 expires. do. In response, the communication unit attempts to resend its configuration request 514 by restarting negotiations. Thus, one or more additional negotiation loops occur before PPP is established, thus delaying call establishment. In the two scenarios shown in Figures 4 and 5, the network element 204 sends control messages (i.e., configuration requests and confirmations) to each peer only in a transparent manner. That is, the network element 204 does not know about the contents of the control messages. This is illustrated in FIG. 1 where PPP messages exchanged by termination protocol layers of peers (communication unit and IWU) pass through an immutable network element.

A flowchart of a method of preventing the problems shown in FIGS. 4 and 5 is shown in FIG. The method shown in FIG. 6 is preferably implemented as software algorithms executed by a network element in an intermediate network. In a preferred embodiment of the present invention, the process shown in Fig. 6 is executed by a base station controller or a mobile switching center as described above. The process shown in FIG. 6 detects when configuration requests are retransmitted and takes appropriate action to avoid additional negotiation loops in response. Note that the method shown in FIG. 6 accommodates the possibility that the problems shown in FIGS. 4 and 5 will occur for any peer.

Beginning at block 602, the network element is configured by messages exchanged between peers to determine if a point-to-point protocol control message is sent by the first peer, in particular by a first peer, eg, a configuration request. Monitor control messages regarding the negotiation phase of a point-to-point protocol session. To do this, the network element does not transparently pass point-to-point protocol messages to their destinations, but instead inspects any messages containing data specified in the PPP layer in the peer. In particular, the network element starts monitoring after the physical links (ie, between the MS and IWU and the network element) are established. Thereafter, the network element examines all packets passing through it and examines packets containing a PPP header indicating status as a control message or a data message. If a control message from the first peer is not detected at block 602, it means that a data message is sent instead, and processing is a block in which the network element waits for a predetermined period of time configurable, typically a few hundred milliseconds. Continue at 604). The particular duration chosen is preferably selected based on the optimal measurements made during system configuration and deployment. In any case, after waiting, the network element determines, at block 606, whether a control message is received from the second peer. Otherwise, it again means that the data message is sent by the second peer to the first peer, which assumes that a point-to-point protocol session has already been established between the peers and the process has ended. In the context of the present invention, this means that monitoring for control messages is stopped until any stored parameters (described above) are discarded and a new call is initiated.

However, if a control message from the first peer is detected at block 602, processing continues at block 608 to determine if the control message is a point-to-point protocol configuration request. If the control message is not a configuration request, this means confirmation, and processing continues at block 612, which stores the parameters included in the confirmation and then sends the confirmation to the intended destination. In practice, the parameters in the confirmation identify the specific configuration request that confirms this. Examples of suitable parameters included in the configuration request and confirmation include identification, magic number, maximum receiving unit, address field compression and IP address. Processing then resumes at block 602, where the network element controls the messages by monitoring the messages between the first and second peers.

If the control message is a configuration request, processing continues at block 610 to determine if the configuration request is a retransmission of a preconfiguration request. If not, it means that the configuration request is such a first request sent by the first peer, and processing continues at step 602. The processing of these blocks identified by reference numerals 602-612 is until the configuration requests are determined or until the session has already been established (eg, as determined by the transmission of data by both peers). It continues until retransmitted by either the first or second peer. If at block 610 it is determined that a retransmitted request was received from either the first or second peer, processing continues at block 614 to determine whether the acknowledgment corresponding to the retransmitted configuration request has been pre-confirmed. . If not, it means that the peer issuing the retransmission request attempts to restart negotiations or start a new negotiation after failing to receive a configuration request from another peer, and processing passes the retransmitted request to its intended destination. Continuing at block 616.

However, if a pre-received retransmitted request is acknowledged, the processing does not merely pass the retransmitted request to the intended destination, but instead processes the retransmitted request itself based on stored parameters from the pre-received acknowledgment. The process continues at block 618. In this preferred embodiment, when processing a retransmitted configuration request, the network element discards the retransmitted request, thereby preventing it from obtaining it at its intended destination, which is directed to the sender of the resent configuration request. The acknowledgment can be sent (optionally, preferably) again. In this way, the network element confirms to the transmitter of the retransmitted configuration request that the negotiation process has been completed successfully, thereby avoiding additional negotiation loops. This is additionally illustrated in connection with FIGS. 7 and 8.

As outlined in circles in Figures 7 and 8, a network element in accordance with the present invention monitors PPP messages sent between peers. Thus, in both FIGS. 7 and 8, the network element stores parameters related to the confirmation sent by the IWU 206 in response to the configuration request sent by the communication unit 202. Thereafter, it acknowledges retransmission 702 of the configuration request by the communication unit. In the scenario of FIG. 7, an undesirable technique is illustrated that simply discards the resent request 702. In this case, the IWU never receives the retransmitted request 702 because it determines that the network element has been previously identified by the IWU. Thus, it retransmits its own configuration request 704, which is passed on the communication unit because it has not been confirmed in advance. Thereafter, the request 704 resent from the IWU is confirmed by the communication unit (706). In contrast, Figure 8 shows a preferred embodiment of sending acknowledgment 802 back to the transmitter of the request, ie the communication unit, resent by the network element. In general, it is desirable to confirm the resent request in order to explicitly terminate the handshake protocol from the perspective of the peer resending the configuration request.

The present invention avoids redundant negotiation loops or handshakes when establishing a PPP session in a wireless network. By monitoring the messages exchanged between the two peers for control messages and storing the relevant parameters, the present invention allows the intermediate network element to be aware of the occurrence of retransmitted configuration requests resulting in dual negotiations and retransmitted requests based on the stored parameters. To avoid the occurrence of additional negotiation loops. In this way, the effects of asynchronous link establishment and different timeout timers are mitigated by the network element.

In the foregoing description, the invention has been described with reference to specific embodiments. However, those skilled in the art will recognize that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are within the scope of the present invention.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, advantages, advantages, solutions to problems and any advantage, advantage or more pronounced solution are not to be construed as important, necessary or necessary features or elements in any claim or the entire claims. As used herein, the term “comprises”, “comprising” or any other variation thereof includes a process, method, article, or apparatus that includes a list of elements, rather than just including these elements. It is intended to mean inclusively that it may include other elements that are not uniquely or expressly listed in the method, article or device.

Claims (11)

In a communication system comprising at least two peers communicating with each other across an intermediate network comprising one or more infrastructure elements, one of the at least one infrastructure elements may be two peers of the at least two peers. In a method for establishing communications between the methods, the method comprises: Monitoring at least some of the messages exchanged between the two peers for control messages; Storing at least some parameters corresponding to the control messages exchanged between the two peers to provide stored parameters; Detecting the occurrence of retransmission of a control message from one of the two peers, wherein the retransmission of the control message results in duplicate negotiations between the two peers; And, Processing the retransmission of the control message based on the stored parameters such that the duplicate negotiations are avoided. The communication system of claim 1, wherein the communication system comprises a wireless communication system, the at least two peers including at least one wireless communication unit communicating with at least one interaction unit via the intermediate network, and the control message. Is transmitted from a wireless communication unit of the at least one wireless communication unit. The control system of claim 1, wherein the communication system comprises a wireless communication system, and wherein the at least two peers comprise at least one wireless communication unit communicating with the at least one interaction unit via the intermediate network, the control And a message is sent from one interaction unit of the at least one interaction unit. The method of claim 1, wherein before detecting retransmission of the control message: Detecting transmission of data by each of the two peers; And, Discarding the stored parameters in response to detecting retransmission of the data by each of the two peers. In a communication system comprising at least two peers communicating with each other across an intermediate network including at least one infrastructure element, one of the at least one infrastructure elements is a first peer of the at least two peers. And a method for establishing communications between a second peer, the method comprising: Receiving a targeted request control message from the first peer to the second peer; Storing parameters from the request control message to provide stored request control message parameters; Forwarding the request control message to the second peer; Receiving a retransmission of the request control message targeted from the first peer to the second peer; And, Processing a retransmission of the request control message based on the stored request control message parameters. 6. The method of claim 5, wherein processing the retransmission of the control message further comprises discarding the retransmission of the control message. 6. The method of claim 5, wherein processing the retransmission of the control message further comprises confirming the retransmission of the control message. 6. The method of claim 5, prior to receiving a retransmission of the first request control message. Detecting transmission of data by each of the first peer and the second peer; And, Discarding the stored request control message parameters in response to the data transmission by the first peer and the second peer. An apparatus for use in an intermediate network that forms part of a communication system, the communication system comprising at least two peers in communication with each other across the intermediate network, the apparatus comprising: At least one processor; And, And at least one storage device coupled to the at least one processor and storing instructions, wherein the instructions are executed by the at least one processor when executed by the at least one processor: Monitor at least some of the messages exchanged between two of the at least two peers for control messages; Store at least one parameter in the at least one storage device corresponding to the control messages exchanged between the two peers to provide stored parameters; Detect the occurrence of a retransmission of a control message from one of the two peers, wherein the retransmission of the control message generates duplicate negotiations between the two peers; And to handle retransmission of the control message based on the stored parameters such that the duplicate negotiations are avoided. 10. The system of claim 9, wherein the at least one storage device is executed by the at least one processor: Instructions for handling the retransmission of the control message by discarding the retransmission of the control message. 10. The system of claim 9, wherein the at least one storage device is executed by the at least one processor: And instructions for handling the retransmission of the control message by confirming the retransmission of the control message.